The entry plan is 3,000 basic words a month and 1,000 advanced words a month. Not 4,000 words. Two separate balances that do not convert into each other, spent by choosing a mode.
The practical difficulty is that the choice arrives before the information needed to make it. You are asked which quality tier to spend on a document before seeing what either produces on that document, and the cheaper balance is four times the size — so the rational move is to spend basic words until they run out, which is also the move that tells you least about what you bought. Run out of advanced words in week two and the plan you are left with is a different, lesser product until the month turns over.
Ours is one number: 25,000 words a month on the $18 plan, spent the same way whatever tone you pick. That is not a cleverer design, it is a simpler one, and simplicity is most of the argument for it. Two-currency pricing is common in this category and it consistently favours the seller, because unspent balances in the smaller currency are revenue.